Method and apparatus for solubilizing humic acid granules

ABSTRACT

Improved methods and apparatus (10, 74) for the solubilization of initially solid humic acids include a large-volume mixing/agitation tank (12, 76) for water and solid humic acids, together a recirculation assembly (14, 78) for continuously recirculating the water/humic acids mixture while reducing the size of the humic acids. Properly used, the apparatus (10, 74) is capable of providing relatively stable, solubilized humic acid solutions or dispersions.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a division of U.S. application Ser. No. 14/948,480filed Nov. 23, 2015, which claims the benefit of U.S. ProvisionalApplication Ser. No. 62/084,864, filed Nov. 26, 2014;

both of these applications are incorporated herein by reference in theirentireties.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention is broadly concerned with methods and apparatusfor reconstituting solid humic acids as relatively stable aqueousdispersions suitable for field application without undue sedimentationof the humic acids. More particularly, the invention is concerned withsuch methods and apparatus wherein a relatively large capacitywater/solid humic acids mixing tank is provided, and equipped with aninternal agitation assembly and an external recirculation assembly.These system components are operated so as to assure rapid and effectivesolubilization of humic acids.

Description of the Prior Art

Humic acids have long been used by gardeners and farmers as fertilizersand soil amendments. These materials are naturally occurring and thusorganic, and have a number of beneficial effects:

-   -   Improves the uptake of nutrients    -   Assists in soil remediation    -   Improves root structure and development    -   Increases microbial activity    -   Boosts seed germination    -   Increases yields    -   Reduces fertilizer runoff    -   Promotes healthier crops    -   Improves water retention    -   Increases antioxidant activity    -   Stimulates plant enzymes    -   Prevents disease and heat stress    -   Enhances soil fertility.

Large-scale agricultural uses of humic acids generally require that theacids be delivered in solid form, typically either as powders orgranules. If humic acids are sold as liquids in such contexts, shippingcosts can be prohibitive. Nonetheless, it is often most convenient toapply humic acids in solubilized form using conventional agriculturalspraying equipment. Accordingly, the ideal situation is that the humicacids be sold and shipped in solid form, and then solubilized on-site bya dealer or farmer prior to application thereof. Another requirement isthat the resultant liquid be relatively stable, without unduesedimentation of the humic acids over extended storage periods.

In practice, it has been found that solubilization of such initiallysolid humic acids can be difficult and sometimes impossible to achieve.This is especially the case where relatively small volumes ofsolubilized product are required. There is accordingly a real andunsatisfied need in the art for improved methods and apparatus wherebyinitially solid humic acids may be quickly and efficiently solubilizedto yield relatively stable final products.

SUMMARY OF THE INVENTION

The present invention overcomes the problems outlined above and providesapparatus for reconstituting and hydrating humic acid originally insolid form as aqueous, relatively stable solutions or dispersions; incertain embodiments, the resultant solutions or dispersions have humicacid solids with average sizes of less than about 400 microns. As usedherein, “humic acids” is a general term which embraces a variety ofspecific acids including fulvic acids, which are generally lowermolecular weight species of humic acids. Therefore, “humic acids” shouldbe taken as a generic term encompassing all such acidic species.

The apparatus includes a water/solid humic acids tank having a liquidinlet and a liquid outlet, a solid humic acid inlet, a volume of atleast about 300 gallons, and a frustoconical lower section with theliquid outlet being adjacent the bottom of the lower section. Arecirculation assembly also forms a part of the apparatus and isoperable to continuously withdraw the water/humic acid mixture from thetank liquid outlet and to recirculate the mixture to the liquid inlet.The recirculation assembly includes a pump equipped with an impeller andcapable of moving the mixture at a rate of at least about 125 gallonsper minute from the liquid outlet to the liquid inlet while reducing thesize of the solid humic acid, and provides a mixture residence time ofat least about 2 minutes within the tank during recirculation. The tankis also equipped with an internal agitation assembly operable to agitatethe mixture; this assembly has an upright shaft and mixing elementssecured to the shaft, and a drive operable to rotate the shaft at a rateof at least about 45 rpm.

The invention also provides methods of reconstituting humic acidscomprising the steps of forming a mixture comprising water and solidhumic acid in a tank having a liquid inlet and a liquid outlet, a volumeof at least about 300 gallons, and a frustoconical lower section withthe liquid outlet being adjacent the bottom of the lower section. Themixture is continuously recirculated from the liquid outlet and to theliquid inlet using a recirculation assembly having a pump equipped withan impeller and capable of recirculating the mixture at a rate of atleast about 125 gallons per minute from the liquid outlet to the liquidinlet. Moreover, the recirculation assembly is designed to allow themixture to reside within the tank for a residence time of at least about2 minutes during the recirculation step. During recirculation, themixture is also agitated within the tank using an agitation assemblyincluding an upright shaft and mixing elements secured to the shaft, androtating the shaft at a rate of at least about 45 rpm.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the preferred apparatus useful in theinvention;

FIG. 2 is a front elevational view of the apparatus;

FIG. 3 is a side elevational view of the apparatus;

FIG. 4 is another side elevational view of the apparatus, illustratingthe side opposite that shown in FIG. 3;

FIG. 5 is a plan view of the apparatus;

FIG. 6 is an exploded view depicting the components of the preferredagitation assembly forming a part of the overall apparatus;

FIG. 7 is a perspective view of another preferred apparatus useful inthe invention;

FIG. 8 is another perspective view of the FIG. 7 apparatus, viewing fromthe opposite side thereof illustrated in FIG. 7; and

FIG. 9 is a sectional view taken along line 9-9 of FIG. 7.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment of FIGS.1-6

Turning now to the drawings, an apparatus 10 for reconstitution of solidhumic acids as aqueous dispersions is illustrated in FIGS. 1-5 andbroadly includes a mixing/agitation tank 12, a recirculation assembly14, a control station 16, and support structure 18 for theaforementioned components. The apparatus 10 is designed to quickly andefficiently solubilize solid humic acids, typically in the form ofgranules and/or powders, to yield humic acid aqueous dispersions whichare relatively stable and can be field-applied using conventionalagricultural spraying equipment for fertilization and/or soilremediation purposes.

In more detail, the tank 12 is formed of synthetic resin material, has acapacity of 345 gallons, and includes an upper cylindrical section 20and a lower frustoconical section 22 terminating with a downwardlyextending outlet valve 24. A top cover assembly 26 is positioned atopcylindrical section 20 and includes an apertured cover plate 28supporting an infeed funnel 30, and a recirculation inlet fitting 32.The assembly 26 further includes a support channel 34 having anagitation drive motor 36 and gear box 38 with a one-inch output shaft,and a removable inspection lid 40 covering an inspection opening (notshown) through the cover assembly. Internally, the tank 12 is equippedwith an agitation assembly 42 (see FIG. 6), which includes an elongated,upright shaft 44 and a plurality of outwardly extending blade-likemixing elements 46. Although the blades as shown are essentially flatand angularly oriented, such blades could also be provided withdownwardly concave surfaces. The shaft 44 is connected via coupler 50 tothe output shaft 52 of gear box 38. As best seen in FIG. 3, the shaft 44is substantially centrally located within tank 12, extending from theconnection with the output shaft of gear box 38 downwardly intoproximity with outlet valve 24.

The recirculation assembly 14 includes a pump 54 having a cast ironcentrifugal pump head and an internal metallic impeller blade (notshown) powered by means of drive motor 56. An elongated, two-inch,reinforced conduit hose 58 is secured to the inlet 60 of pump 54 and toa tee connector 62. The valve 24 is a full-port, three-way, two-inchball valve, and is secured to the frustoconical section 22 of tank 12.Additionally, the assembly 14 includes an upwardly extending outputconduit 64 having an intermediate two-way valve unit 66. The lower endof conduit 64 is secured to the output 68 of pump 54 and to therecirculation inlet fitting 32 supported by cover assembly 26. Finally,a delivery tube 69 is secured to fitting 32 and extends downwardly intothe confines of tank 12 (FIG. 2).

The control station 16 includes an upstanding channel 70, which supportsa rotatable operating handle 72 as well as push-button electroniccontrols 74. The handle 72 is operably connected with the valve unit 66in order to permit manual operation thereof between recirculation anddischarge positions, whereas the controls 74 are electrically connectedto conventional sensors forming a part of apparatus 10.

The support structure 18 includes a lowermost metallic base 76 equippedwith forklift tongue openings 78. A series of upright support posts 80extend upwardly from base 76 with lateral reinforcing elements 81interconnecting the posts. Four oblique struts 82 also extend upwardlyfrom the base 76 and are secured to a collar 83. The collar 83 isequipped with four obliquely upwardly extending tank supports 83a. Inthis fashion, the support structure 18 presents a cradle designed toremovably support the tank 12. As also shown, the base 76 supportschannel 70, pump 54, and motor 56. In this fashion, the entire apparatus10 is portable and can be moved within a plant as needed in order to mixand solubilize solid humic acids.

In the operation of apparatus 10, water and solid humic acids aredelivered to tank 12 via funnel 30, and motor 36 is energized to rotatethe shaft 44, thereby agitating the humic acid/water mixture within thetank. After a suitable period of mixing, the recirculation assembly 14is actuated by energizing pump motor 56 and opening the valve unit 66 tothe “recirculation” position. This causes the humic acid/water mixturewithin tank 12 to be drawn through hose 58, pump 54, and conduit 64, sothat the mixture is ultimately delivered through the tube 69 within theconfines of the tank. These agitation and recirculation operations arecontinued until the initially solid humic acids are substantiallysolubilized. At this point, during continued operation oftherecirculation assembly 14, the operating handle 72 is moved to the“discharge” position, whereby the solubilized humic acids are deliveredvia an output conduit (not shown) operably coupled with the remainingend of valve unit 66.

In the development of the invention, it has been found that, in order toefficiently solubilize humic acids and create stable dispersions, atleast some important parameters outlined below should be employed in theuse of apparatus 10. Otherwise, humic acid solubilizations proceed atunacceptably slow rates and/or the humic acids never becomesatisfactorily solubilized.

For example, these parameters include the volumetric size of the tank12, which should be at least about 300 gallons, and more preferably fromabout 325-375 gallons. The recirculation pump 54 advantageously has astainless steel impeller, which is operable to handle and break down thesolid humic acids as they pass through the pump. The pump is rated atleast about 125 gallons per minute, and more preferably from about150-210 gallons per minute. The recirculation apparatus 14 is preferablyoperated so that the mixture within tank 12 has a residence time of atleast about two minutes, more preferably about 2.3 minutes. Theagitation assembly 42 is preferably operated at a rate of at least about45 rpm, and more preferably from about 50-65 rpm. The mixing elements 40serve to submerge and agitate the solid humic acids to therebyfacilitate solubilization thereof. The presence of the discharge tube69, having its lowermost outlet end below the level of liquid within thetank 12, prevents foaming of the mixture which may be occur if therecirculating mixture were simply added to the top of the liquid withinthe tank. As noted, the conduit 58 is reinforced so as to preventcollapse thereof owing to the suction of pump 54. It is to be understoodthat not all of these parameters in combination need be used to achievesatisfactory results, but at least some of them should be employed forbest results.

Proper use of apparatus 10 yields relatively stable solubilized humicacid solutions or dispersions which resist undue sedimentation for atleast about three days, and more preferably at least about one week; asused herein “undue sedimentation” refers to more than about 10% byweight of the humic acid content of the products collecting as sedimentwithin a container for the solutions or dispersions.

Embodiment of FIGS. 7-9

FIGS. 7-8 illustrate another suitable apparatus 74 for carrying out theinvention, which broadly includes a mixing tank 76, a recirculationassembly 78, a control station 80, and support structure 82. The tank 76may be formed of any suitable material, such as metal or syntheticresin, and includes an upper cylindrical section 84 and a lowerfrustoconical section 86. The tank is also equipped with a tank topcover 88 including a port 90 having a hinged cover 92, a U-shaped vent94, and an inlet elbow 95 equipped with valve 95 a.

The recirculation assembly 78 includes a centrifugal pump 96 coupled toa motor 98. An inlet conduit 100 is operably coupled to the pump inlet,whereas an outlet conduit 102 extends upwardly from the pump outlet andextends through tank top cover 88, terminating in a horizontal deliverypipe 104 within the confines of tank 76. The conduit 102 includes anintermediate stub pipe 106 having a valve 108.

The control station 80 includes an upright standard 110 supporting aprogrammable digital control box 112 and a sensor module 114, the latterhaving a lead 116 attached to a level sensor 118 which passes throughtank section 84 to communicate with the interior of tank 76.

The bottom frustoconical section 86 of tank 76 has a central verticallyextending outlet tee 120. One leg of the tee 120 includes a valve 122coupled with the end of conduit 100, whereas the other tee leg has avalve 124 that may be used to empty the contents of tank 76 without theneed for operation of pump 96.

The support structure 82 includes four upright legs 126 as well as amotor/pump stand 128, the latter also supporting standard 110.

Operation of the apparatus 74 involves continuous recirculation of waterand humic acids through tee 120, conduit 100, pump 96, conduit 102, andoutlet pipe 104 until the desired degree of humic acid solubilizationhas been achieved. Advantageously, use of the apparatus 74 involvesfilling the tank 76 with water to a level indicated by sensor 118,followed by operation of pump 96 to recirculate the water. Then, anappropriate quantity of humic acid solids are introduced into the tank76 via port 90 and allowed to recirculate with the water for a period oftime to hydrate the solids. Additional quantities of humic acid solidsare then added over time, with increasing pump speeds to achieve thedesired fully hydrated and solubilized, smooth, and lump-free product.

The apparatus 74 has the same preferred parameters described inconnection with the embodiment of FIGS. 1-6, including the tank size,pump design and throughput rates, and residence time within the tank.However, it has been found that the embodiment of FIGS. 7-9 does notrequire a separate agitation assembly. Notwithstanding the absence of anagitation assembly, the apparatus 74 is capable of producing the stablesolubilized humic acid solutions or dispersions described previously.

We claim:
 1. An apparatus for reconstituting humic acid in solid form inaqueous form, comprising: a fixed-dimension tank having inlet structurefor water and solid humic acids in the form of granules and/or powders,and a liquid outlet, said tank having a volume of at least about 300gallons, and a lower section with said liquid outlet being adjacent thebottom of the lower section; a recirculation assembly operable towithdraw a water and humic acid mixture from said liquid outlet and torecirculate the mixture to said inlet structure and into the confines ofsaid tank, said recirculation assembly including a pump equipped with animpeller and capable of moving said mixture at a rate of at least about125 gallons per minute from said liquid outlet to said inlet structurewhile reducing the size of said solid humic acid, said recirculationassembly providing a humic acids solids residence time of at least about2 minutes within said tank for said mixture during said recirculation;and a motor-driven mixing shaft extending into the confines of said tankand operable to agitate said mixture during recirculation thereof by therecirculation assembly.
 2. The apparatus of claim 1, said pump ratebeing about 150 gallons per minute.
 3. The apparatus of claim 1, saidtank having a frustoconical lower section.
 4. The apparatus of claim 1,said residence time being 2.3 minutes.
 5. The apparatus of claim 1, saidvolume being about 345 gallons.
 6. The apparatus of claim 1, including adischarge tube within said tank and extending downwardly from said inletstructure a distance so that said mixture is discharged below the levelof liquid within the tank.
 7. The apparatus of claim 1, including areinforced conduit between said tank outlet and the inlet of said pump,which prevents contraction of the conduit during operation of theapparatus.
 8. The apparatus of claim 1, said agitation assemblyincluding an upright shaft and mixing elements secured to said shaft,and a drive operable to rotate the shaft at a rate of at least about 45rpm.
 9. The apparatus of claim 1, said apparatus operable to create anaqueous solution of humic acid solids having an average size of lessthan about 400 microns.
 10. The apparatus of claim 1, said apparatusoperable to create an aqueous solution of humic acid solids whichexhibits no more than about 10% by weight sedimentation of the humicacid content of the solution for at least about one week.
 11. Theapparatus of claim 1, said inlet structure including separate inlets forsaid solid humic acid and water, respectively.